.app-container {
  max-width: 100%;
  margin: 0 auto;
  text-align: center;
  padding: 20px;
}

.grid {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.grid-row {
  display: flex;
  margin-bottom: 8px; /* 给行之间增加一点间距 */
}

.grid-cell {
  width: 30px; /* 格子宽度 */
  height: 30px; /* 格子高度 */
  text-align: center;
  border: 1px solid red; /* 红色边框 */
  margin: 0; /* 去掉格子间的间隙 */
  font-size: 20px;
  line-height: 30px;
  outline: none;
  background-color: #fff;
}

.grid-cell:focus {
  background-color: #f0f0f0;
}

.buttons {
  margin-top: 20px;
}

button {
  padding: 8px 16px;
  margin: 5px;
  border: none;
  background-color: #4caf50;
  color: white;
  cursor: pointer;
}

button:hover {
  background-color: #45a049;
}

.controls {
  margin-bottom: 20px;
  display: flex;
  justify-content: center;
  align-items: center;
}

#row-selector {
  margin-left: 10px;
  padding: 5px;
  font-size: 16px;
}
